Recent decades have seen a wave of institutional changes of the core democratic rules in advanced democracies. These changes include reforms of electoral systems; decentralization of power to subnational governments; the creation or enhancement of direct-democratic institutions; a rise in public subsidies to political parties; and shifts in the balance of power between executive and legislature. Nevertheless, political science has developed a limited understanding of what explains institutional change in democracies that are already consolidated. This is partly due to the lack of comparative data on the subject, with most studies of institutional change focusing on a single country, or on a single type of reform (e.g. electoral system change). Our paper seeks to bridge this gap by presenting the preliminary findings of an international research project that compared seven dimensions of institutional change in 18 consolidated European democracies between 1990 and 2008, producing a unique dataset whose content has been fully verified by national experts. This dataset provides the empirical basis for evaluating the type and extent of institutional change in consolidated European democracies, as well as developing hypotheses about the motivations and calculations behind these reforms.